This invention relates to a novel technology for use in cooling systems for fuel cell powered vehicles and/or equipment. In order to remove the heat that is generated in fuel cell systems, 1,3-propane diol is used as the chemical base for the heat exchange fluid.
It has been suggested that fuel cell technology can be used to generate electricity in sufficient volume to be applicable in the driving of electric motors for passenger vehicles, standby power generation, and other applications. A fuel cell is a device that converts chemical energy of a fuel directly into electricity and they are intrinsically more efficient than most other energy generation devices, such as internal combustion engines. In principle, a fuel cell operates somewhat like a battery. Unlike a battery, a fuel cell does not run down or require recharging. It will produce energy in the form of electricity and heat as long as fuel is supplied. The most common type of fuel cell consists of two electrodes sandwiched around an electrolyte. Oxygen passes over one electrode and hydrogen over the other, generating electricity, water, and heat.
The fact that heat is generated by the fuel cell requires the presence in the automobile or other system of a cooling system which can be similar to those used presently in internal combustion engines. Typically, such a system includes a circulating pump, plumbing that may include aluminum, brass, copper, lead-tin solder, stainless steel, plastic or rubber materials, and a heat exchanger (radiator) typically constructed of aluminum or copper/brass.
The heat exchange fluid (coolant) is obviously just as important in a fuel cell system as it is in internal combustion engines. Many of the requirements of a heat exchange fluid for internal combustion engines are also required for fuel cell engines. However, there are some additional requirements. For instance, fuel cell vehicles generate a direct current of 400 volts. The coolant, which flows around the aluminum components of the fuel cell, must be nonconductive to protect both the cell itself from shorting out and to prevent electrical hazard to humans operating or servicing the system.
The first fuel cell was built in 1839 by Sir William Grove, a Welsh judge and gentleman scientist. The xe2x80x9cGrove cellxe2x80x9d used a platinum electrode immersed in nitric acid and a zinc electrode in zinc sulfate to generate about 12 amps of current at about 1.8 volts. There were other developments in fuel cell technology over the years but serious interest in the fuel cell as a practical generator of electricity did not begin until the 1960""s, when the U.S. Space Program chose fuel cell technology over nuclear power and solar energy. This technology, developed by Francis Thomas Bacon, used nickel gauze electrodes and operated under pressures as high as 300 psi.
A nontoxic fuel cell engine coolant which has an electrical resistivity of greater than 250 kOhm-cm, a boiling point of greater than 90xc2x0 C., optionally, a freezing point of less than xe2x88x9240xc2x0 C., a thermal conductivity of greater than 0.4 W/m-k, a viscosity of less than 1 cPs at 80xc2x0 C., a viscosity of less than 6 cPs at 0xc2x0 C., a heat capacity of greater than 3 kJ/kg-K, and which is compatible with current cooling system materials. The coolant may contain from 1 to 100, preferably 40 to 85 and most preferably 55 to 85, volume percent PDO and most or all of the remaining balance is water.